I heard Unity is also good.
It's...a little too large in the size of the file for my comfort. If it is too confounding for me to understand, I would likely drop it to maintain the will to work on this project, and that would be a great deal of data used up.
The other thing you are going to have to decide is simply speaking is how you are going to handle the age aspect of Dragons.
Whether it will be gradual aging with changes in its art at certain intervals... Or if there will be "Stages of life" that will be sudden and bring up the new rules of the game.
Now the reason why Life Stages instead of Gradual aging is a possible choice, in my mind, is that it allows you to stage the content simply by playing off the dragon's size. So a hatchling dragon would be in small caves and glenns and every age basically shoves the dragon out of its smaller and smaller world.
It also lets to stage different elements of the game as they come so as not to overwhelm the newer player.
Gradual Aging though has a more organic approach and is less jarring allowing for the feel of steadily growing along with the game.
All of the ideas I have go more along the lines of Gradual Aging, with the character image starting out as small within the game grid, then growing to fill the entirety of that grid space, before expanding into covering a 2x2 grid, before slowly growing to fill that, reaching 3x3. This would continue until a point (yet to be determined).
Note: Images of others would be scaled. 1x1 would have small entitiess, ex. lizards and chickens. 2x2 would have larger entities, such as dogs and humans. 3x3 would have even larger entities, such as horses and trolls.
Though I ultimately keep thinking of treasure and how important that is for a dragon (Who are hoarders) and I cannot think of much other then making it be EXP.
I guess it could be tied into some sort of reputation system as sort of a status symbol.
Ohh well, tis all I can think of. I am trying to think of options mostly.
I'll likely tie it to reputation.